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大兴安岭林区地处寒温带。其气候特点是寒冷而较干燥,尤其是北部,长冬无夏,并有岛状分布的永并层。在多年冻土区调查中发现,兴安落叶松有一部分根系伸展至冻土中,其形成原因是当地面上无树木生长时,由于无树冠覆盖蔽荫,地温升高,致使连续冻土层融化深度较深,冻土上界面下降,为兴安落叶松生长创造了条件。但是,当树木生长起来后,由于树木遮光作用,致使地温降低,冻土上界面上升,抑制了落叶松生长,形成“老头树”。据测定,在生长季节地温仅5—8℃。
Daxinganling forest is located in cold temperate. Its climatic features are cold and dry, especially in the north, long winter without summer, and there are island-shaped distribution of eternal layer. In the permafrost survey found that part of Larix gmelinii root system extends into the frozen soil, the reason is that when there is no tree growth on the ground, because no tree cover shade, ground temperature, resulting in continuous frozen soil layer Deep melting depth, the permafrost interface on the decline, for the growth of larch to create the conditions. However, when the trees grow up, the ground temperature is reduced due to the shading effect of the trees, the interface of the permafrost rises, and the growth of the larches is inhibited, forming the “old tree.” It is determined that in the growing season ground temperature is only 5-8 ℃.